The invention relates to a safety helmet with a crown made of material resistant to mechanical shocks, containing a lining cap separated from the peak of the crown by an insulating gap, a securing device having a head-band with a flexible annular strip arranged away from the edge of the crown to grip the circumference of the user's head, and means for adjusting the length of the head-band comprising:
- a first mechanism with operating inverter pinion cooperating simultaneously with a first crown-wheel and a second crown-wheel located respectively at the two opposite ends of the strip,
- a first operating device accessible from outside and able to be grasped in the fitted position of the helmet on the user's head, said operating device being in mechanical connection with the inverter pinion, and being formed by a rotating ring comprising a spindle on which the inverter pinion is mounted, which is arranged to transform the rotation movement of the ring into two reverse sliding movements of the two crown-wheels resulting in an increase or decrease of the length of the head-band depending on the direction of rotation of the ring.
State-of-the-art means for adjusting the head-band make use of a loop fixed to one of the ends of the band or strap, and designed to cooperate with the other free end. The loop is located inside the crown and adjustment of the head-band requires the helmet to be taken off and both hands to be used. Several operations are generally necessary before the correct adjustment is found. Another drawback of the adjusting loop results from the decentering effect of the head-band with respect to the mid-axis of the crown, generated when a variation of the useful length of the annular band is made. These drawbacks are detrimental to the speed of adjustment, and convenience of use.
Adjustment of the head-band by means of an inverter pinion and double crown-wheel mechanism is already known from the documents U.S. Pat. No. - A 3,329,968 and U.S. Pat. No. - A 4,888,831. The mechanism is however located at the rear of the crown, resulting in permanent engagement of the head against the front part of the crown. Axial centering of the head with respect to the vertical mid-axis of the helmet is not ensured.
The object of the invention consists in improving adjustment of the securing device when the helmet is fitted on the user's head.